Demand for wireless communication services, such as mobile telephones in cellular and Personal Communications Service (PCS) systems, is continually increasing. Meanwhile, the Global Positioning System (GPS) is gaining widespread acceptance in numerous commercial applications. GPS includes a network of satellites which permit users equipped with GPS receivers to determine their position anywhere in the world with a high degree of accuracy. Position determination is also an important issue in wireless communication systems, in that it is often desirable for the wireless system to determine the positions of mobile telephones or other types of mobile communication stations. A wireless system which is able to determine the position of a given mobile station in an efficient manner could provide an enhanced level of service to the user, while also generating additional revenue for a service provider.
As an example of the need for mobile position determination in a wireless system, consider a scenario in which a mobile telephone user is traveling on an unfamiliar highway. The mobile telephone user enters the highway and passes several exits in traveling toward a destination. The user then experiences car trouble, pulls the car off the road, and makes a call from the mobile telephone to an emergency road service. The user attempts to describe the location to the emergency service operator, but unfortunately does not remember the last exit number that was just passed on the highway. The user may therefore be forced to ask the police to conduct a wide area search in order to receive the road service. The feeling of frustration and helplessness experienced by the user would be compounded if the car trouble occurred late at night, in inclement weather or in a high-crime area.
The increasingly widespread use of both wireless systems and GPS receivers suggests that mobile position determination in a wireless system could be provided using the capabilities of GPS. A "brute force" approach to utilizing GPS functions to provide mobile position determination in a wireless system could involve simply integrating a conventional GPS receiver into each mobile station. However, this brute force approach unduly increases the cost, size, weight and power consumption of the mobile station, and is therefore not likely to be commercially viable. Similar simplistic approaches attempting to integrate various conventional GPS features into the mobile station may tend to require the introduction of complex, multilayer user interface functions, thereby undermining the efficiency of the wireless system. Unfortunately, there does not appear to be any currently available technique suitable for integrating GPS-like functions into a wireless system in a cost-effective manner and without degrading voice quality.
As is apparent from the above, a need exists for a mobile position determination technique which may be configured to utilize GPS-like functions, requires minimal additional mobile station and base station circuitry, does not require multilayer user interface functions, and does not degrade voice quality in the wireless system.